Atoms, the fundamental building blocks of matter, consist of a positively charged nucleus surrounded by a cloud of negatively charged electrons. The positive charge of the nucleus is normally offset exactly by the negative charge of the surrounding electrons. However, in some elements the electron arrangement makes it convenient to lose or gain an electron. This results an atom with a net charge, an ion. Many examples of ionized atoms exist.

Electron Orbitals

Electrons occupy very distinct energy levels with respect to the positively charged nucleus. These energy levels are known as orbitals. Each orbital can occupy a fixed number of electrons. For example, s-orbitals can hold two electrons and p-orbitals can hold six electrons. In atoms, filled orbitals are energetically more favorable than partially filled orbitals.

Sodium

You can find the element sodium in group 1 of the periodic table. It has 11 positively charged protons and 11 negatively charged electrons. There is only one electron in the outer orbital of sodium, and its loss would lead to a more stable electron configuration with a completely filled 2p-orbital. The loss of sodium's outer electron means that it becomes ionized with a single positive charge. The symbol for ionized sodium is Na+.

Chlorine

You can find the element chlorine in group 17 of the periodic table. It has 17 positively charged protons and 17 negatively charged electrons. The outer 3p-orbital of chlorine possesses five electrons. A 3p-orbital with six electrons would be a stable orbital configuration. Chlorine atoms often become ionized by gaining an electron in order to stabilize their outer orbital configuration. The addition of an electron means that chlorine becomes ionized with a negative charge. The symbol for ionized chlorine is Cl-.

Calcium

You can find the element calcium in group 2 of the periodic table. It has 20 positively charged protons and 20 negatively charged electrons. The outer 4s-orbital of calcium contains two electrons. Calcium can become ionized by losing one or two electrons. The loss of 1 electron leads to a calcium ion with a net positive charge of +1, while the loss of two electrons leads to a calcium ion with a net positive charge of +2. The symbol for ionized calcium is Ca+ or Ca2+, depending upon the number of electrons lost.

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About the Author

Samuel Markings has been writing for scientific publications for more than 10 years, and has published articles in journals such as "Nature." He is an expert in solid-state physics, and during the day is a researcher at a Russell Group U.K. university.